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The Royal College of Psychiatrists Improving the lives of people with mental illness


Seasonal Affective Disorder (SAD)

IntroductionSeasonal affective disorder 2

Some of us notice that we don't feel so good in the winter months, particularly if we live somewhere where the climate changes a lot and it is dark during the winter.

This feeling can interfere with your life - some people say that it feels "like hibernation".

This is what we call Seasonal Affective Disorder (SAD). The term "Winter Depression" and "Winter Blues" has also been used to describe this.


What is Seasonal Affective Disorder (SAD)?

SAD has a lot in common with depression. Have a look at our general leaflet on Depression before reading this leaflet.


The main symptoms of SAD are similar to those of depression, but happen in the winter.


  • low mood 
  • lack of interest and enjoyment in life

Often also these symptoms occur also:

  • low energy
  • being less sociable
  • being less irritable
  • less interest in sex.

Common symptoms of SAD which are different from those in most depression are:

  • sleeping more
  • eating more.

If you have  SAD, you may find it hard to wake up on a winter's morning and can often feel sleepy during the day. You may crave chocolate and high carbohydrate foods, such as white bread or sugary foods. You might find you put weight on.


SAD gets better in the spring. Indeed, around a third of people with SAD have a time when they feel more energetic than usual during the spring and summer.


Who is affected by SAD?

Like other types of depression, SAD is most common in women during the years when they can have children.  It is about three times more common in women than it is in men.  SAD is less common in children and in older adults, affecting men and women equally.


How common is it?

Many of us will feel different in the winter with symptoms of feeling slightly tired, sleeping a bit more and perhaps gaining some weight.  It is a bit like hibernation in animals. If your symptoms are bad enough to interfere with your life, you may well have SAD.  In the UK, about 3 people in every 100 have significant winter depressions.


What causes SAD?

We do not fully understand what causes SAD, but the reduced amount of light in the winter seems to be important. It is more common where it is dark in the winter. There has been a lot of research exploring how daylight can influence appetite, wakefulness and mood.


However, people living in very northern areas do not appear to suffer more SAD than people living further south, so other factors may be important. Also, some people report that they feel depressed in the summer instead.


Managing SAD

SAD can be treated in the same way as depression. Treatment usually includes self-help and lifestyle changes, talking therapies and antidepressant medication. Light box treatments are also popular and have some evidence.



Some symptoms of SAD can create extra problems which make you feel even worse – 'vicious circles':

  • If it is dark and you feel tired all the time, you will probably do less – and this can make SAD worse. Try to get as much natural sunlight as possible. Take a walk during daylight hours or carry on any exercise you would normally do. Remind yourself that days will get longer again in the spring.
  • If you are eating more, you may put on too much weight which makes you feel worse. Remind yourself that most people put on weight in autumn and early winter.
  • Sleepiness, lack of motivation and irritability can all cause problems at home, with your friends, and at work. The feelings of not getting things done can make you feel stressed. Tell your family and friends so that they can understand what is happening and be supportive.

Light therapy

The idea is to try to provide extra light and to make up for the shortage of daylight in winter. A "light box" is used. Its light is like sunlight, but without the ultraviolet rays, so it is not harmful to the skin or the eyes. It may help tell the brain to make less of a hormone, melatonin.


A light box is usually used for 30 minutes to an hour each day. It is most helpful if you use it at breakfast time. Light therapy works quite quickly. If it is going to help, most people will notice some improvement in the first week.


Fortunately, any side-effects are usually mild. They include headache, nausea or blurred vision. It is usually best not to use a light box after 5.00 pm because you may then find it hard to get to sleep.


Dawn-simulating alarm clocks are also used. These come on dimly about an hour before waking up time and gradually get brighter. They can be helpful if you find it hard to wake up on winter mornings.



Antidepressants may be helpful in SAD. Any medication which would make people more tired or sleepy should be avoided, and so SSRI antidepressants are usually used (more details in our leaflet on antidepressants).  The best evidence is for the use of sertraline, citalopram or fluoxetine.  In SAD, it is usual to start antidepressants in the autumn and stop them in the spring. A recent review of the evidence did not find a large effect, but you ask your doctor.


Cognitive behavioural therapy (CBT)

There is some evidence that CBT can help winter depression and may prevent it coming back in future winters. CBT is a treatment for anxiety and depression in general. You have weekly sessions with a therapist and do some homework, like keeping a diary. Have a look at our leaflet on CBT.


What is the best treatment?

For mild symptoms, the self-help measures described in this leaflet will usually be enough.

If your symptoms are worse, the first choice is usually between a light box and antidepressants. The choice will often depend on what is available, what is convenient and what you prefer.


Further information

Light boxes

There are numerous companies selling light boxes, and some will offer a trial-and-return so you can return it if it is not helpful. Search on the internet or contact SADA.

CBT Resources


Anonymous (2009) Management of seasonal affective disorder. Drugs and Therapeutic Bulletin, 47, 128-132.

Golden, BN et al (2005) The efficacy of light therapy in the treatment of mood disorders:  a review and meta-analysis of the evidence.  American Journal of Psychiatry, 162, 656-662.


Eagles, JM (2009) Light therapy and seasonal affective disorder. Psychiatry, 8, 125-129.

Thaler K, Delivuk M, Chapman A, Gaynes BN, Kaminski A, Gartlehner G. Second-generation antidepressants for seasonal affective disorder. Cochrane Database of Systematic Reviews 2011, Issue 12.

Johnsen et al.: Is there a negative impact on mental distress and sleeping problems in the sub-artic? Findings from the cross-sectional Tromsø Study. BMC Psychiatry 2012 12:225.

Produced by the Royal College of Psychiatrists' Public Engagement Editorial Board.

Series editor: Dr Philip Timms

Original author: Professor John Eagles

Reviewed by Dr Wojtek Wojcik and Dr Robin Berger

Service user/carer input: Depression Alliance

Illustration: Lo Cole:

This leaflet reflects the best available evidence available at the time of writing.

© April 2015. Due for review: April 2018. Royal College of Psychiatrists. This leaflet may be downloaded, printed out, photocopied and distributed free of charge as long as the Royal College of Psychiatrists is properly credited and no profit is gained from its use. Permission to reproduce it in any other way must be obtained from The College does not allow reposting of its leaflets on other sites, but allows them to be linked to directly.

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